BEIRUT — Syria’s government appeared to distance itself from further engagement with the special peace envoy of the United Nations and Arab League on Thursday, declaring him ‘‘flagrantly biased’’ even as his efforts aimed at a political transition to end the nearly two-year Syrian conflict were accelerating.

The efforts by the special envoy, Lakhdar Brahimi, include a planned meeting in Geneva on Friday with top diplomats from the two superpowers on opposite sides of the Syria conflict: the United States, which supports the insurgency, and Russia, which supports the Syrian government but has increasingly displayed ambiguity about support for President Bashar Assad.

A statement from the Foreign Ministry denouncing Brahimi appeared to be a response to remarks he had made to Western news agencies the day before in which he suggested that Assad must relinquish power and could not be part of any replacement government in Syria.

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The verbal back-and-forth came as new flare-ups of insurgency violence hit Idlib Province in northwest Syria, where rebel fighters were reported to have raided an important air base housing helicopters and warplanes that Assad’s military has been using to attack rebel-held territory and to resupply soldiers.

A government opponent said the military was blowing up thee aircraft preemptively to prevent insurgents from gaining access to them. Despite the increased range of weaponry used by the rebels, who include a number of defecting air force pilots, they have no aircraft.

New signs of civilian desperation were emerging Thursday as well in the Syrian refugee camps of neighboring countries, particularly Jordan, where the UN children’s agency issued an unusually blunt appeal for help at a mud-soaked encampment housing more than 54,000 Syrians, most of them women and children.

The Syrian criticism of Brahimi, a veteran Algerian statesman who spent days talking with Assad and other Syrian officials in Damascus last month, raised the possibility that he, like his predecessor, Kofi Annan, could be sidelined into irrelevance by the antagonists in the conflict, who have shown little or no interest in dialogue as the violence has worsened. At least 60,000 people have been killed in Syria since the uprising against Assad began in March 2011, the United Nations said last week.

Brahimi told the BBC on Wednesday that Syrians want the Assad family to go after four decades in power. He told Reuters that he saw no place for Assad in any political transition.

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Syria’s Foreign Ministry said in a statement Thursday that such remarks were a surprise and showed that Brahimi ‘‘is flagrantly biased for those who are conspiring against Syria and its people.’’ The ministry statement suggested that Syria’s government had lost whatever faith it might have reserved for Brahimi. Still, it did not specifically declare unwillingness to work with him.

The Syrian insurgent assault on the Idlib air base, the Taftanaz military airport, lasted for hours and included fighters from the jihadist groups Jabhet al-Nusra and Ahrar al-Sham, according to accounts from government foes.